Michael Sears

Michael Sears
Arizona State University | ASU

Doctor of Philosophy

About

69
Publications
16,534
Reads
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5,264
Citations
Additional affiliations
July 2009 - June 2012
Bryn Mawr College
Position
  • Professor (Assistant)

Publications

Publications (69)
Article
Full-text available
Hybridization between species affects biodiversity and population sustainability in numerous ways, many of which depend on the fitness of the hybrid relative to the parental species. Hybrids can exhibit fitter phenotypes compared to the parental lineages, and this ‘hybrid vigour’ can then lead to the extinction of one or both parental lines. In thi...
Article
Full-text available
Although predators can deter an animal from regulating its body temperature by basking or shuttling, this response to predation should depend on the spatial distribution of thermal resources. By simulating predation risk, we showed that movement, thermoregulation and corticosterone of male lizards (Sceloporus jarrovi) depended on the spatial distri...
Article
Full-text available
A core challenge in global change biology is to predict how species will respond to future environmental change and to manage these responses. To make such predictions and management actions robust to novel futures, we need to accurately characterize how organisms experience their environments and the biological mechanisms by which they respond. Al...
Preprint
Full-text available
A challenge in global change biology is to predict how species will respond to future environmental change and to manage these responses. To make such predictions and management actions robust to novel futures, we need to accurately characterize how organisms experience their environments and the biological mechanisms by which they respond. All org...
Article
Full-text available
Rapid global change has increased interest in developing ways to identify suitable refugia for species of conservation concern. Correlative and mechanistic species distribution models (SDMs) represent two approaches to generate spatially‐explicit estimates of climate vulnerability. Correlative SDMs generate distributions using statistical associati...
Article
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Traits often contribute to multiple functions, complicating our understanding of the selective pressures that influence trait evolution. In the Chihuahuan Desert, predation is thought to be the primary driver of cryptic light coloration in three White Sands lizard species relative to the darker coloration of populations on adjacent dark soils. Howe...
Article
Although climate warming poses a grave threat to amphibians, little is known about the capacity of this group to evolve in response to warming. The capacity of key traits to evolve depends on the presence of genetic variation on which selection can act. Here, we use repeatability estimates to estimate the potential upper bounds of heritable genetic...
Article
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Background: High-quality genomic resources facilitate investigations into behavioral ecology, morphological and physiological adaptations, and the evolution of genomic architecture. Lizards in the genus Sceloporus have a long history as important ecological, evolutionary, and physiological models, making them a valuable target for the development...
Preprint
Full-text available
High-quality genomic resources facilitate population-level and species-level comparisons to answer questions about behavioral ecology, morphological and physiological adaptations, as well as the evolution of genomic architecture. Squamate reptiles (lizards and snakes) are particularly diverse in characteristics that have intrigued evolutionary biol...
Article
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Physiological acclimation has the potential to improve survival during climate change by reducing sensitivity to warming. However, acclimation can produce trade-offs due to links between related physiological traits. Water loss and gas exchange are intrinsically linked by the need for respiratory surfaces to remain moist. As climates warm and dry,...
Article
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Organisms rely upon external cues to avoid detrimental conditions during environmental change. Rapid water loss, or desiccation, is a universal threat for terrestrial plants and animals , especially under climate change, but the cues that facilitate plastic responses to avoid desiccation are unclear. We integrate acclimation experiments with gene e...
Article
Over the past decade, ecologists and physiologists alike have acknowledged the importance of environmental heterogeneity. Meaningful predictions of the responses of organisms to climate will require an explicit understanding of how organismal behavior and physiology are affected by such heterogeneity. Further, the responses of organisms themselves...
Article
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For more than 70 years, Hutchinson's concept of the fundamental niche has guided ecological research. Hutchinson envisioned the niche as a multidimensional hypervolume relating the fitness of an organism to relevant environmental factors. Here, we challenge the utility of the concept to modern ecologists, based on its inability to account for envir...
Article
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When offspring share a womb, interactions among fetuses can impart lasting impressions on phenotypic outcomes. Such intrauterine interactions often are mediated by sex steroids (estrogens and androgens) produced by the developing fetuses. In many mammals, intrauterine interactions between brothers and sisters lead to masculinization of females, whi...
Article
Hormones such as glucocorticoids and androgens enable animals to respond adaptively to environmental stressors. For this reason, circulating glucocorticoids became a popular biomarker for estimating the quality of an environment, and circulating androgens are frequently used to indicate social dominance. Here, we show that access to thermal resourc...
Article
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Extinction rates are predicted to rise exponentially under climate warming, but many of these predictions ignore physiological and behavioral plasticity that might buffer species from extinction. We evaluated the potential for physiological acclimatization and behavioral avoidance of poor climatic conditions to lower extinction risk under climate c...
Article
The capacity to tolerate climate change often varies across ontogeny in organisms with complex life cycles. Recently developed species distribution models incorporate traits across life stages; however, these life-cycle models primarily evaluate effects of lethal change. Here, we examine impacts of recurrent sublethal warming on development and sur...
Article
1.Reversible acclimation increases resilience to environmental stress, but acclimation may have hidden costs due to underlying links between related physiological traits. Interactions between physiological traits might result in trade-offs that undermine whole-organism performance if the change in a related trait reduces the net benefits of acclima...
Article
Christian et al. (2017) proposed several possible flaws in the methods and logic presented by Riddell et al. (2017) that included potential activity of salamanders during measurements, trimming of the agar model's legs, misinterpretations of the empirical data, limitations on agar models, and the relationship between body size and skin resistance t...
Article
Species ranges are constrained by the physiological tolerances of organisms to climatic conditions. By incorporating physiological constraints, species distribution models can identify how biotic and abiotic factors constrain a species’ geographic range. Rates of water loss influence species’ distributions, but characterizing water loss for an indi...
Article
Although most organisms thermoregulate behaviorally, biologists still cannot easily predict whether mobile animals will thermoregulate in natural environments. Current models fail because they ignore how the spatial distribution of thermal resources constrains thermoregulatory performance over space and time. To overcome this limitation, we modeled...
Article
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When predicting the response of organisms to global change, models use measures of climate at a coarse resolution from general circulation models or from downscaled regional models. Organisms, however, do not experience climate at such large scales. The climate heterogeneity over a landscape and how much of that landscape an organism can sample wil...
Article
Metabolic rates are correlated with many aspects of ecology, but how selection on different aspects of metabolic rates affects their mutual evolution is poorly understood. Using laboratory mice, we artificially selected for high maximal mass-independent metabolic rate (MMR) without direct selection on mass-independent basal metabolic rate (BMR). Th...
Article
For many organisms, constraints on activity increase energetic costs, which ultimately reduce the suitability of a particular habitat. Mechanistic species distribution models often use estimates of activity to predict how organisms will respond to climate change. These models couple physiology and morphology with climatic data to estimate potential...
Article
Full-text available
For many organisms, constraints on activity increase energetic costs, which ultimately reduce the suitability of a particular habitat. Mechanistic species distribution models often use estimates of activity to predict how organisms will respond to climate change. These models couple physiology and morphology with climatic data to estimate potential...
Article
In recent years, ecologists have stepped up to address the challenges imposed by rapidly changing climates. Some researchers have developed niche-based methods to predict how species will shift their ranges. Such methods have evolved rapidly, resulting in models that incorporate physiological and behavioral mechanisms. Despite their sophistication,...
Article
Full-text available
Reduction in body size is a major response to climate change, yet evidence in globally imperiled amphibians is lacking. Shifts in average population body size could indicate either plasticity in the growth response to changing climates through changes in allocation and energetics, or through selection for decreased size where energy is limiting. We...
Conference Paper
Background/Question/Methods: Climate change models project widespread range contractions for Appalachian salamanders within the next decade, with greatest effects predicted for species in the southern Appalachians. Climate change can impact amphibians through shifts in species distributions, leaner body condition, and reduced growth. These impacts...
Article
Physiological ecologists have long sought to understand the plasticity of organisms in environments that vary widely among years, seasons and even hours. This is now even more important because human-induced climate change is predicted to affect both the mean and variability of the thermal environment. Although environmental change occurs ubiquitou...
Article
Although climates are rapidly changing on a global scale, these changes cannot easily be extrapolated to the local scales experienced by organisms. In fact, such generalizations might be quite problematic. For instance, models used to predict shifts in the ranges of species during climate change rarely incorporate data resolved to <1 km(2), althoug...
Article
On a global scale, changing climates are affecting ecological systems across multiple levels of biological organization. Moreover, climates are changing at rates unprecedented in recent geological history. Thus, one of the most pressing concerns of the modern era is to understand the biological responses to climate such that society can both adapt...
Article
Schwenk and colleagues challenged biologists to develop a deeper understanding of the linkages between organisms and environments. These linkages are captured by the concept of the niche, which has guided theoretical and empirical research in ecology for decades. Despite this research, we still cannot explain or predict much of the variation in nic...
Article
Full-text available
Most organisms experience environments that vary continuously over time, yet researchers generally study phenotypic responses to abrupt and sustained changes in environmental conditions. Gradual environmental changes, whether predictable or stochastic, might affect organisms differently than do abrupt changes. To explore this possibility, we expose...
Conference Paper
Background/Question/Methods Understanding the responses of plants and animals to ongoing climate change is one of the most pressing questions for a practicing ecologist today. Over the past century, global climates have warmed and climatic models predict continued warming in the near future. Warmer temperatures will directly impact organisms give...
Article
Ecology Letters (2010) 13: 1041–1054 Two major approaches address the need to predict species distributions in response to environmental changes. Correlative models estimate parameters phenomenologically by relating current distributions to environmental conditions. By contrast, mechanistic models incorporate explicit relationships between environm...
Article
When animals consume less food, they must reduce their body temperature to maximize growth. However, high temperatures enhance locomotion and other performances that determine survival and reproduction. Therefore, thermoregulatory behaviors during different metabolic states reveal the relative importance of conserving energy and sustaining performa...
Article
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Because temperature affects the growth, development, and survival of embryos, oviparous mothers should discriminate carefully among available nesting sites. We combined a radiotelemetric study of animal movements with a spatial mapping of environmental temperatures to test predictions about the nesting behavior of the eastern fence lizard (Scelopor...
Article
Full-text available
The genetic variances and covariances of traits must be known to predict how they may respond to selection and how covariances among them might affect their evolutionary trajectories. We used the animal model to estimate the genetic variances and covariances of basal metabolic rate (BMR) and maximal metabolic rate (MMR) in a genetically heterogeneo...
Conference Paper
Background/Question/Methods Batrachochytrium dendrobatidis (Bd) is a fungal pathogen causing amphibian population declines. Bd has a narrow thermal tolerance and requires moisture to survive. Differences in frog biology, pathogen biology and/or environment may determine population response to disease. Population responses to Bd vary among sites, ha...
Article
Understanding the links between physiological performance and fitness is key to predicting the responses of individuals to environmental change, especially that imposed by climate. Of particular interest are traits linked with metabolic performance. In particular, maximal metabolic rate (MMR; which describes the upper limit to heat production) and...
Article
Full-text available
We review the evidence for the role of climate change in triggering disease outbreaks of chytridiomycosis, an emerging infectious disease of amphibians. Both climatic anomalies and disease-related extirpations are recent phenomena, and effects of both are especially noticeable at high elevations in tropical areas, making it difficult to determine w...
Data
List of Monteverde Specimens Examined for Bd (32 KB DOC)
Article
Full-text available
Urbanization has caused regional increases in temperature that exceed those measured on a global scale, leading to urban heat islands as much as 12 degrees C hotter than their surroundings. Optimality models predict ectotherms in urban areas should tolerate heat better and cold worse than ectotherms in rural areas. We tested these predications by m...
Conference Paper
Patterns of field body temperatures exhibited by gravid female squamate reptiles often deviate from those exhibited by non-gravid females or males. Typically, oviparous females choose cooler temperatures when gravid, while viviparous females choose warmer temperatures when gravid. Assuming that animals choose body temperatures to maximize fitness,...
Article
Understanding an animal's ecology requires knowledge of how individual variation in behaviour and physiology interact with each other and with the environment that an animal experiences. Environmental variation affects behaviour, but whether individual variation in physiological performance also affects behaviour is poorly known. We studied a high‐...
Article
Thermal constraints on the time available for activity have been proposed as a proximate mechanism to explain variation in suites of life history traits. The longer that an ectotherm can maintain activity, the more time it has to forage and the greater chance that it will encounter a predator and be eaten. Thus, the thermal environment may produce...
Article
Along an elevational gradient on SW Utah, sagebrush lizards (Sceloporus graciosus) exhibit an unexpected pattern of growth. Lizards from a high elevation population grow faster than lizards from two populations at lower elevations despite shorter daily and seasonal activity. Results from a common environment study of growth suggest that the differe...
Article
Although most species of animals examined to date exhibit Bergmann's clines in body size, squamates tend to exhibit opposing patterns. Squamates might exhibit reversed Bergmann's clines because they tend to behaviorally regulate their body temperature effectively; the outcome of this thermoregulation is that warmer environments enable longer daily...
Article
The majority of ectotherms grow slower but mature at a larger body size in colder environments. This phenomenon has puzzled biologists because classic theories of life-history evolution predict smaller sizes at maturity in environments that retard growth. During the last decade, intensive theoretical and empirical research has generated some plausi...
Article
Current theories predict the thermal adaptation of both maternal and embryonic phenotypes such that the fitness of the entire life cycle is maximized. Our studies of the eastern fence lizard (Sceloporus undulatus) have generated evidence that maternal and embryonic phenotypes are designed to promote growth and development in cold environments. Fema...
Article
We performed a laboratory common-environment study to determine the genetic and environmental sources of variation in growth rates of the sagebrush lizard (Sceloporus graciosus). Hatchling lizards were reared from gravid females collected from three study populations along an elevational gradient in southern Utah, USA. Hatchlings were fed ad libidu...
Article
Fence lizards, Sceloporus undulatus, reproduce multiple times per year. Surival of reproducing females drops dramatically between clutches from first to final clutch of the year. Also, offspring from later clutches emerge with less time available for growth and storage prior to hibernation. Considering these two facts, life history theory predicts...
Article
Geographically widespread species often exhibit variation in life history traits that are a result of differences in the quality and abundance of available resources. Documented body size patterns among populations of sagebrush lizards (Sceloporus graciosus) show that large body size in free-ranging lizards is associated environments that provide l...
Article
1. Studies of reproductive effort in ectotherms have focused primarily on the energetic investment in gamete production; much less is known about the indirect energetic costs of reproduction, such as increased metabolic costs of maintenance or activity. 2. The metabolic cost of reproduction in the oviparous lizard, Sceloporus undulatus, was investi...

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